Equivalency between quantity of firewood, volume in stere (depending size cut of log), related weight and energetic power

stère de bois Auteur Julo (Wikimedia) Stere (or stère) is a unit of volume used to measure the quantity of firewood. It is an apparent volume of 1 cubic metre for 1 metre long wood logs. so a pile of 1 metre high, 1 metre large and 1 metre deep.

When you cut wood, it takes less space because it is easier to fill gaps. Apparent volume is then less.
For example, a stere of wood uses 1 cubic metre occupied by 1 metre long logs ; but you cut these logs in half, each of them will be 50 cm long, they will take a volume of about 0.8 m3 because it is easier to fill the gaps.

So there is an equivalence between various quantities of wood depending on log sizes, so you can compare prices according to size, or your provider can give logs of different sizes if he doesn't have enough size of ordered size (take care they still fit in your fireplace, stove or heating...).

When wood is humid, it is heavier. The norm is to dry wood for 2 years before burning it because green or humid wood has a poor energetic performance. It needs 18 months in a ventilated shelter to get a humidity of 20 %.

Fireplaces with inserts have a much better energetic performance than open fireplaces (and anyway, open fireplace pollutes 8 times more particles). Some areas want to regulate the use of open fireplaces.

The energetic power of dry wood per weight is about the same (4 kWh/kg at 20% humidity) for any kind of wood (including bark) but some wood is heavier so the energy quantity varies per unit of volume.
In Europe, the highest quality of wood includes a mix of 95 % of hornbean , oak and European beech, very heavy woods which burn slowly with a good ember.

With the following array, you can easily compute the equivalence between an invoiced volume in stere and the apparent volume. It also gives an equivalent weight and heat of combustion, so the energetic power of combustion.

As it is energy, it is also compared to petrol equivalent.

Enter a value in the second column of the following array and the conversion will be performed automatically in all other units.


stere of wood, invoiced volume st
(also apparent volume in m3 for logs 1 metre long)
(also length of storage in metres - 1 metre high for logs of 1 metre deep)
US and Canadian cord (128 cubic feet, 3.62 steres)
European cord (4 steres)
apparent volume for logs of 50 centimetres m3 (50)
also length of storage in metres - 1 metre high for logs of 50 centimetre deep ml (50)

apparent volume for logs of 45 centimetres m3 (45)
also length of storage in metres - 1 metre high for logs of 45 centimetre deep ml (45)

apparent volume for logs of 40 centimetres m3 (40)
also length of storage in metres - 1 metre high for logs of 40 centimetre deep ml (40)

apparent volume for logs of 33 centimetres m3 (33)
also length of storage in metres - 1 metre high for logs of 33 centimetre deep ml (33)

apparent volume for logs of 30 centimetres m3 (30)
also length of storage in metres - 1 metre high for logs of 30 centimetre deep ml (30)

apparent volume for logs of 25 centimetres m3 (25)
also length of storage in metres - 1 metre high for logs of 25 centimetre deep ml (25)

apparent volume for logs of 20 centimetres m3 (20)
also length of storage in metres - 1 metre high for logs of 20 centimetre deep ml (20)

Approximative weight for dry wood (2 years, mix of oak, beech, hornbeam) kg
Approximative weight for dry wood (1 year, mix of oak, beech, hornbeam) kg
Approximative weight for fresh wood (mix of oak, beech, hornbeam) kg
approximative heat of combustion (*) for dry wood (2 years, humidity 20%, 4.3 kWh/kg) kWh
approximative heat of combustion (*) for fresh wood (humidity 60%, 1.7 kWh/kg) kWh
heat of combustion (*) for dry hornbeam (2172 kWh/st) kWh
heat of combustion (*) for dry oak (1957 kWh/st) kWh
heat of combustion (*) for dry european beech (1930 kWh/st) kWh
heat of combustion (*) for dry ash (1834 kWh/st) kWh
heat of combustion (*) for dry birch (1700 kWh/st) kWh
heat of combustion (*) for dry robinia (1680 kWh/st) kWh
heat of combustion (*) for dry chestnut (1600 kWh/st) kWh
heat of combustion (*) for dry pine tree (1212 kWh/st) kWh
Ton of oil equivalent 11 630 kWh) toe
Oil barrel (158.987294928 litres so 1849 kWh) bl

Equivalency between the volume, weight and heat of combustion for compacted sawdust like pellet fuel

Pellet fuel is usually like a small cylinder with a 5 to 6 mm diameter and 6 cm long, they are made of very dry compacted wood, like saw dust.

As humidity is low (below 10%, they have good heat performance (between 4.7 and 5.3 kWh/kg).

Heavy, they dive if you put them in water, but as there is air between pellets when they are stored in bulk, volumic weight is about 675 kg/m3.

Please make sure you store them away from humidity to keep good energetic efficiency.

Pellet volume in cubic metres m3
Pellet volume in litres l
Weight for standard pellets stored in bulk at 675 kg/m3 kg
Approximative heat of combustion (humidity <10%, 5 kWh/kg) kWh

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